Toolholding spindle for die-lapping machines



Sept. 11, 1951 PASTELL 2,567,299

TOOL-HOLDING SPINDLE FOR DIE-LAPPING MACHINES Filed July 6, 1948 [Wei afar: DEWEY P475 TELL,

Patented Sept. 11, 1951 um rso emu-r oFFicE q ,rootuotmre Q 7 MA NES DeweyPastelL'Winthrop Harbonlll. v Application July 6, 1948', Serial No. 37,285.. V l t V 1 Claim,

. :L Ihis invention relates to .asihollo'w sspindleyf or holding a rotary tool and, in particular, to a spindle for a die-lapping machine and improved means for yieldably mounting the -tool therein.

Gang .lapping machines, such as are usedior opening wire-drawing dies, have a plurality of tool-holding spindles mounted in. a head which is movable vertically toward. and from a worksupporting table .therebelow. A lapping tool is inserted in .each spindlev and extendsv therethrough so its point .will en age. a blank-omthe table. If the. tools are fixed in the spindles, they are caused to engage the blanks under such pressure that the flapping is inaccurate and the life of the tools is short. These results are .,e,voided by permitting the tools to float in the spindles, as disclosed in Sengenberger Patent No. 2 $66,062, but a longer time is required to complete the lapping operation.

I have invented novel means for mounting the shank of a lapping tool in a driving spindle whereby the feed of the tool toward the work is positive yet cushioned so that the lapping progresses rapidly and is done accurately, but the tools/have a long useful life. In a preferred embodiment, I provide a driving spindle with yielding collars or rings of rubber or the like seated therein and spaced therealong, adapted to embrace the tool shank snugly with a frictional fit. These rings apply a limited positive thrust to the tools as thevertically movable head descends to bring the tool points into engagement with the work, but yield under a predetermined back pressure, thereby preventing excessive pressure of the tool on the work. The rings also transmit driving torque by friction from the spindle to the tool without slippage.

A complete understanding of the invention may be obtained from the following detailed description which refers to the accompanying drawings illustrating the preferred embodiment. In the drawings,

Figure 1 is a partial vertical section through a spindle for holding and driving a lapping tool, having the invention incorporated therein; and

Figure 2 is a similar view of a portion of the spindle showing a further novel feature of the invention.

Referring in detail to the drawings and for the present to Figure 1, vertically spaced plates I0 and II constitute the crosshead of a lapping machine and may be secured together by spacer bolts in the manner shown in Patent No. 2,366,062. The crosshead is mounted, as shown therein, for vertical reciprocation toward and of spindles, each la p n w one suc p ndl !5 1s Sho n h r in- Thespindle lapping machines of the t'ypeherein contemplated a u u l y provided .with a mu tiplic ty ada t d to receive the shank of For'the sake of simplicity, only tubular, having a bore therethrough. lt is journaled in anti-friction bearings I6 and I1 seat d in s a e holes in the pl te wa d I and secured therein by retainers l6. Eelt rin'gs -:!.9a .0ve and below the retainers is are held in P ey meta e s 0- A sea in v. inef .21 is jdispgse l w t e ea n It and a cover above e b ar n l .beari ss 5 nd H a e mainta ed n perly The inner aces f he spacedrelation by a spacer-sleeve 2 3 f tting snug ly on the spindle l5. A driving 'pul'ley"24"'is mounted on the sleeve and is secured to the spindle by a set screw, extending radially thereof and through a hole in the sleeve.

Circumferential recesses or grooves 25 are formed in the bore through the spindle l5 adjacent the ends thereof and rings or washers 2B of rubber or like material are seated therein. A lapping tool 2'! is inserted through the bore in the spindle and is'frictionally engaged by the inner edges of the rings 26. The tool shank has ample clearance for free movement in the bore through the spindle. The normal inside diameter of the rings 26, however, is slightly less than the diameter of the tool shank, thereby effecting a snug fit of the rings on the shank.

The point of the tool 21 is adapted to engage the blank [4 intermittently as the crosshead is reciprocated at a frequency of several hundred vibrations per minute. As the cross-head descends, bringing the tool point into engagement with the work, the rings 26 transmit limited axial force to the tool, causing it to exert a certain pressure on the blank. As soon as the back pressure equals this amount, the rings 26 flex because of the yielding character of the material of which they are composed, permitting limited axial movement of the tool in the spindle bore and preventing further substantial increase in the pressure. As stated in the patent aforementioned, the overall stroke or throw of the crosshead is only a small fraction of an inch and the yielding of the rings 26 is sufiicient with such a limited movement to relieve excess tool pressure which would otherwise result therefrom. As the cross-head ascends, the rings, of course, restore the tool to normal position.

Figure 2 shows a further improvement in the spindle for mounting and driving the lapping tool. In this form of the invention, the ends of the spindle are counterbored and tapped to accommodate bushings or glands 28. These glands serve to hold the rings 26 in the grooves 25. They also serve to compress the rings slightly when desired to cause radial contraction thereof for adjusting their frictional grip on the tool shank. This makes it possible to compensate for such slight wear of the inside periphery of the rings as may result from long continued use thereof.

It will be evident from the foregoing that the invention provides a tool-holding spindle for lapping machines having several advantages over machines known previously. The principal advantage, of course, is that a limited positive downward force is exerted on the lapping tool through the yielding rings as the crosshead descends. rings cushions the engagement of the tool with the blank and prevents excessive pressure from being'applied to the tool. As a result, the lapping is rapidly and accurately done and the tool is preserved in effective condition throughout a long, useful life. The frictional grip exerted on the tool shank by the yielding rings is ample to transmit the relatively low torque necessary from the driving spindle to the tool. The tool may be easily removed from the spindle, however, when desired, for the purpose of grinding, and as readily replaced.

Although I have illustrated and described but a preferred embodiment of my invention, it will be recognized that changes in the details and arrangement thereof may be made without departing from the spirit of the invention or the scope of the appended claim.

In a die-lapping machine, a spindle journaled for rotation and mounted for reciprocation toward and from a die-blank holder, said spindle having an axial bore therein, a lapping tool having a shank smaller than said bore inserted into the later, a pair of washers of rubber-like materialfixed in said bore at points spaced therealong, the inner edge of each Washer fitting snugly around said shank and being adapted to flex under thrust applied to the tool as a result of engagement with a die blank on the holder, thereby permitting limited axial movement of the tool in said bore while constantly tending to restore it to normal position and thus cushioning repeated engagements of the tool with the blank.

At the same time the yielding of the DEWEY PASTELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 469,052 Wood Feb. 16, 1892 812,549 Cotton et al Feb. 13, 1906 1,800,254 Holmes Apr. 14, 1931 2,285,956 Weber June 9, 1942 2,366,062 Sengenberger Dec. 26, 1944 2,417,249 Griswold Mar. 11, 1947 2,426,200 Green Aug. 26, 1947 FOREIGN PATENTS Number Country Date 109,231 Great Britain of 1917 

